The primary aim of the present study is to determine the impact of being an only child compared with having siblings (older, younger, or both; same or opposite sex) upon interpersonal competence and interpersonal orientation in late adolescence. Specifically, the proposed project will determine the impact of family constellation upon global measures of competence, empathy, androgynous sex role development, additional personality characteristics, and orientations toward family, toward privacy, and toward adults versus peers. Secondary aims include a determination of variations in family cohesion, family interaction patterns, and parenting styles as a function of family constellation. The project will be conducted in two stages. During the first stage, questionnaire information will be obtained from all entering freshmen and their parents at Texas Tech University and the University of Arizona. This information will include background characteristics of students and parents, and scales designed to assess interpersonal competence and family environment. A subsample of 700 of these students will then be selected, based upon family constellation and background characteristics, to participate in an extended assessment of competence including behavioral observations in two situations. In both stages of the study, only children will be compared with other subgroups based upon family size, ordinal position, and sibling gender. Controls are included for such factors as socio-economic status, intelligence, and parents' desired family size.